Title page for ETD etd-05042010-020229

Initial wrist posture during typing as a function of keyboard height and slope

Degree

Master of Science

Department

Industrial and Systems Engineering

Advisory Committee

Advisor Name

Title

Woldstad, Jeffrey C.

Committee Chair

Kemmerling, Paul T. Jr.

Committee Member

Kroemer, Karl H. E.

Committee Member

Keywords

Electronic data processing

Date of Defense

1992-09-05

Availability

restricted

Abstract

Carpal tunnel syndrome has been linked to occupations which use a
computer workstation. Two factors thought to be responsible for this problem
are repetition and awkward wrist postures. This experiment examined wrist
flexion-extension, radial-ulnar deviation, and pronation-supination for 24 righthanded
subjects at 25 combinations of keyboard height and slope. Keyboard
heights tested were: -10, -5, 0, 5, and 10 cm from elbow height, and keyboard
slopes tested were: -45, -22, 0, 22, and 45 degrees from horizontal. Keyboard
slopes were considered negative if they sloped away from the subject and
positive if they sloped towards the subject. Subjects wore a wrist monitor,
comprised of metal strips with potentiometers, on each hand and typed a text
passage for two minutes in each experimental condition. The number of correct
words per minute was also measured in each experimental condition.

Results indicated that flexion was minimum when the keyboard was 45
degrees from horizontal, and that overall the left wrist exhibited extension while
the right wrist exhibited flexion. Ulnar deviation was minimized when the
keyboard height was -10 cm below elbow height, and both ulnar and radial
deviation were minimized at slope conditions 22 and 45 degrees from
horizontal. Higher keyboard heights coupled with positive slopes reduced radial
and ulnar deviation as did lower keyboard heights coupled with negative slopes.

For low keyboard heights, the right hand exhibited more extreme ulnar deviation
than the left hand. Pronation was minimum when the keyboard was 10 cm
above elbow height and -45 degrees from horizontal, and was maximum when
the keyboard was -5 cm below operator elbow height and 45 degrees from
horizontal. Correct words typed per minute was maximun1 at 0 degrees from
horizontal, and decreased quadratically as slope was both increased and
decreased.